(1) Field of the Invention
The present invention relates to an apparatus and a method for preventing the ingress of water into an underwater gun before, during, and after the firing of a projectile.
(2) Description of the Prior Art
Underwater weapons are known in the art. U.S. Pat. No. 3,323,457 to Biehl et al., U.S. Pat. No. 3,453,763 to Barr et al., U.S. Pat. No. 3,580,172 to Hendricks and U.S. Pat. No. 3,158,062 to Feiler illustrate some of these underwater weapons. Keeping the barrel of the weapon clear of water is important to underwater gun operation because it reduces the energy required to eject the projectile or bullet, it increases the muzzle velocities that can be achieved, and it reduces the strength requirements and thus the weight of the barrel.
In the Biehl et al. patent, the underwater weapon comprises a device for launching a projectile. One end of the projectile is covered by a frangible diaphragm. The diaphragm is used to maintain the watertightness of the launcher. In operation, the projectile within the launcher is ejected through the frangible diaphragm. The Barr et al. patent relates to an underwater pistol having a rotatable cylindrical magazine. During operation of this pistol, a projectile is driven through a frangible, and fully removable, sealed front barrel cover. The Hendricks patent also illustrates an underwater weapon in which a projectile resides within a launch tube or barrel having a removable plug affixed at one end to prevent the ingress of water.
The Feiler patent relates to an underwater missile container and launcher which includes a device for maintaining an internal pressure within the launcher which is substantially equal to the pressure of the surrounding environment. The launcher further includes a cap over the launch tube which prevents the ingress of water prior to the launch.
Other devices are known in the art to render firearms waterproof. U.S. Pat. No. 3,677,132 to Plenge illustrates a muzzle attachment for the barrel of a firearm. The muzzle attachment includes a device for sealing it behind a bullet passing therethrough to prevent the escape of expanding gases. This device takes the form of a plurality of polyurethane discs sandwiched between flat metallic washers and spaced apart by ring members. The plugs are X-slotted on both faces thereof for permitting a bullet to pass therethrough without fragmenting or rupturing the element. The disc or plug automatically closes and reseals itself after a bullet has been fired. When the muzzle attachment is threadably engaged with the gun barrel, the weapon is waterproof from the barrel end thereof. U.S. Pat. No. 5,105,571 to Kinchin et al. also relates to a method and apparatus for preventing moisture from entering a firearm. In this patent, lightweight plastic covers are disclosed for use as seals for the openings of a firearm such as the muzzle opening or the magazine well opening. The plastic covers are removable through manual operation. It is also possible to remove the covers by actually firing the weapon.
U.S. Pat. No. 4,848,209 to Almeras discloses sealing a driving apparatus for an underwater device. The apparatus includes a barrel holder, a barrel for guiding a fastener intended to be driven by the gases of a propulsive charge and a percussion system for setting of the charge. The barrel of the device is closed by a closure device made by a material which may be perforated by the projectile disposed inside the tubular element or gun barrel.
U.S. Pat. No. 4,742,775 to Harris illustrates still another approach for sealing an end of an underwater device. In the Harris patent, a sealing compound is used to prevent water from penetrating the casing.
Despite the existence of these devices for sealing and pressurizing underwater weapons and the like, there is still a need for a more efficient approach for preventing the ingress of water into a gun barrel and, in particular, to an approach wherein a series of shots can be fired without water entering the weapon.